Hydroxyalkyl Ether

The hydroxyl groups can be alkylated in the usual manner. Hydroxyalkyl ethers may be prepared with alkylene oxides and chloromethyl ethers by reaction with formaldehyde and hydrogen chloride (86). The terminal chlorides can be easily converted to additional ether groups. 

Starch Ethers. A large number of starch ethers have been prepared and patented only a few are manufactured and used commercially. Commercially available starch ethers are the hydroxyalkyl ethers, hydroxyethylstarch [9005-27-0] and hydroxypropylstarch [9049-76-7] and cationic starches. 

In one process to produce highly activated cellulose for acetylation, cellulose is treated with NaOH (mercerization) followed by a hydroxyalkylating agent, eg, ethylene oxide or propylene oxide, to give a cellulose hydroxyalkyl ether with a DS of 0.05—0.3 (76). The resulting water-insoluble material is highly reactive to conventional acetic anhydride—sulfuric acid acetylation. 

Amylopectin is the polymeric component of starch and consists mainly of glucose units joined at the 1,4-positions. Relative molar mass tends to be very high, e.g. between 7 and 70 million. A variety of modified starches are used commercially which are produced by derivatisation to give materials such as ethanoates (acetates), phosphates, and hydroxyalkyl ethers. Modified and unmodified starches are used in approximately equal tonnages, mainly in papermaking, paper coatings, paper adhesives, textile sizes, and food thickeners. 

A demulsifier composition that is a blend of (1) a propoxylated-ethoxylated block copolymer of a bis-hydroxyalkyl ether and (2) a propoxylated-ethoxylated block copolymer of 2-hydroxymethyl-1,3-propanediol has been described [1750,1751]. 

The blend is partially crosslinked with a vinyl monomer when dissolved in an organic aprotic solvent and has a pH of 5.0 or lower. The first block copolymer is prepared by polycondensing a bis-hydroxyalkyl ether, such as dipropylene glycol, diethylene glycol, and the like, with propylene oxide. Next, the resulting propoxylated diol is reacted with ethylene oxide to produce the block copolymer. The second copolymer is prepared by polycondensing 2-amino-2-hydroxymethyl-1,3-propanediol, commonly known as TRIS, with... 

The reagent of choice for the reduction of ketals to ethers is alone prepared in situ from lithium aluminum hydride and aluminum chloride in ether. At room temperature ethers are obtained in 61-92% yields [792, 934]. Cyclic ketals prepared from ketones and 1,2- or 1,3-diols afford on hydrogenolysis by alanes alkyl P- or y-hydroxyalkyl ethers in 83-92% yields [792]. 

Scheme 5. Liquid-crystal behavior of hydroxyalkyl ethers.

J. Gagnaire, G. Toraman, G. Descotes, A. Bouchu, and Y. Queneau, Synthesis in water of amphiphilic sucrose hydroxyalkyl ethers, Tetrahedron Lett., 40 (1999) 2757-2760. 

Table 2 shows that in addition to THF (1), ethers and an acetal such as diethyl ether (7), oxetane (9), 2-methyltetrahydrofuran (12) and 1,3-dioxolane (11) undergo a-C-H hydroxyalkylation to provide adducts in good yields. Dibutyl ether (8) (64% yield dr 71 29) and oxepane (10) (63% yield dr 88 12) have also been found to afford a-hydroxyalkylated ethers under the same conditions in moderate yields [20], It is interesting to note that the reaction selectively provides threo alcohols (entries 1-5). Occasionally, ethyl adducts and/or 4-methoxybenzylalcohol are produced, but the amounts of the byproducts are usually negligible. 

Some beer bottle manufacturers have added poly(vinyl alcohol) to the adhesive to ensure resistance to iced water yet retain washability in the bottling operation. Others have used the starch paste to extend the more water-resistant casein adhesives (0). Newer adhesives are being developed based on double treatments of starches such as hydroxyalkyl ethers of oxidized starch, blending these products with other specified polymers (12,13) or adding synthetic resins... 

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